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Message-Id: <d20f15f7241892ab7f042a8361103287aaf6a83f.1592338450.git.dcaratti@redhat.com>
Date: Tue, 16 Jun 2020 22:25:20 +0200
From: Davide Caratti <dcaratti@...hat.com>
To: Po Liu <Po.Liu@....com>, Cong Wang <xiyou.wangcong@...il.com>,
Vladimir Oltean <olteanv@...il.com>
Cc: "David S. Miller" <davem@...emloft.net>, netdev@...r.kernel.org
Subject: [PATCH net v3 1/2] net/sched: act_gate: fix NULL dereference in tcf_gate_init()
it is possible to see a KASAN use-after-free, immediately followed by a
NULL dereference crash, with the following command:
# tc action add action gate index 3 cycle-time 100000000ns \
> cycle-time-ext 100000000ns clockid CLOCK_TAI
BUG: KASAN: use-after-free in tcf_action_init_1+0x8eb/0x960
Write of size 1 at addr ffff88810a5908bc by task tc/883
CPU: 0 PID: 883 Comm: tc Not tainted 5.7.0+ #188
Hardware name: Red Hat KVM, BIOS 1.11.1-4.module+el8.1.0+4066+0f1aadab 04/01/2014
Call Trace:
dump_stack+0x75/0xa0
print_address_description.constprop.6+0x1a/0x220
kasan_report.cold.9+0x37/0x7c
tcf_action_init_1+0x8eb/0x960
tcf_action_init+0x157/0x2a0
tcf_action_add+0xd9/0x2f0
tc_ctl_action+0x2a3/0x39d
rtnetlink_rcv_msg+0x5f3/0x920
netlink_rcv_skb+0x120/0x380
netlink_unicast+0x439/0x630
netlink_sendmsg+0x714/0xbf0
sock_sendmsg+0xe2/0x110
____sys_sendmsg+0x5b4/0x890
___sys_sendmsg+0xe9/0x160
__sys_sendmsg+0xd3/0x170
do_syscall_64+0x9a/0x370
entry_SYSCALL_64_after_hwframe+0x44/0xa9
[...]
KASAN: null-ptr-deref in range [0x0000000000000070-0x0000000000000077]
CPU: 0 PID: 883 Comm: tc Tainted: G B 5.7.0+ #188
Hardware name: Red Hat KVM, BIOS 1.11.1-4.module+el8.1.0+4066+0f1aadab 04/01/2014
RIP: 0010:tcf_action_fill_size+0xa3/0xf0
[....]
RSP: 0018:ffff88813a48f250 EFLAGS: 00010212
RAX: dffffc0000000000 RBX: 0000000000000094 RCX: ffffffffa47c3eb6
RDX: 000000000000000e RSI: 0000000000000008 RDI: 0000000000000070
RBP: ffff88810a590800 R08: 0000000000000004 R09: ffffed1027491e03
R10: 0000000000000003 R11: ffffed1027491e03 R12: 0000000000000000
R13: 0000000000000000 R14: dffffc0000000000 R15: ffff88810a590800
FS: 00007f62cae8ce40(0000) GS:ffff888147c00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f62c9d20a10 CR3: 000000013a52a000 CR4: 0000000000340ef0
Call Trace:
tcf_action_init+0x172/0x2a0
tcf_action_add+0xd9/0x2f0
tc_ctl_action+0x2a3/0x39d
rtnetlink_rcv_msg+0x5f3/0x920
netlink_rcv_skb+0x120/0x380
netlink_unicast+0x439/0x630
netlink_sendmsg+0x714/0xbf0
sock_sendmsg+0xe2/0x110
____sys_sendmsg+0x5b4/0x890
___sys_sendmsg+0xe9/0x160
__sys_sendmsg+0xd3/0x170
do_syscall_64+0x9a/0x370
entry_SYSCALL_64_after_hwframe+0x44/0xa9
this is caused by the test on 'cycletime_ext', that is still unassigned
when the action is newly created. This makes the action .init() return 0
without calling tcf_idr_insert(), hence the UAF + crash.
rework the logic that prevents zero values of cycle-time, as follows:
1) 'tcfg_cycletime_ext' seems to be unused in the action software path,
and it was already possible by other means to obtain non-zero
cycletime and zero cycletime-ext. So, removing that test should not
cause any damage.
2) while at it, we must prevent overwriting configuration data with wrong
ones: use a temporary variable for 'tcfg_cycletime', and validate it
preserving the original semantic (that allowed computing the cycle
time as the sum of all intervals, when not specified by
TCA_GATE_CYCLE_TIME).
3) remove the test on 'tcfg_cycletime', no more useful, and avoid
returning -EFAULT, which did not seem an appropriate return value for
a wrong netlink attribute.
v3: fix uninitialized 'cycletime' (thanks to Vladimir Oltean)
v2: remove useless 'return;' at the end of void gate_get_start_time()
Fixes: a51c328df310 ("net: qos: introduce a gate control flow action")
CC: Ivan Vecera <ivecera@...hat.com>
Signed-off-by: Davide Caratti <dcaratti@...hat.com>
---
net/sched/act_gate.c | 36 +++++++++++++-----------------------
1 file changed, 13 insertions(+), 23 deletions(-)
diff --git a/net/sched/act_gate.c b/net/sched/act_gate.c
index 9c628591f452..94e560c2f81d 100644
--- a/net/sched/act_gate.c
+++ b/net/sched/act_gate.c
@@ -32,7 +32,7 @@ static ktime_t gate_get_time(struct tcf_gate *gact)
return KTIME_MAX;
}
-static int gate_get_start_time(struct tcf_gate *gact, ktime_t *start)
+static void gate_get_start_time(struct tcf_gate *gact, ktime_t *start)
{
struct tcf_gate_params *param = &gact->param;
ktime_t now, base, cycle;
@@ -43,18 +43,13 @@ static int gate_get_start_time(struct tcf_gate *gact, ktime_t *start)
if (ktime_after(base, now)) {
*start = base;
- return 0;
+ return;
}
cycle = param->tcfg_cycletime;
- /* cycle time should not be zero */
- if (!cycle)
- return -EFAULT;
-
n = div64_u64(ktime_sub_ns(now, base), cycle);
*start = ktime_add_ns(base, (n + 1) * cycle);
- return 0;
}
static void gate_start_timer(struct tcf_gate *gact, ktime_t start)
@@ -287,12 +282,12 @@ static int tcf_gate_init(struct net *net, struct nlattr *nla,
enum tk_offsets tk_offset = TK_OFFS_TAI;
struct nlattr *tb[TCA_GATE_MAX + 1];
struct tcf_chain *goto_ch = NULL;
+ u64 cycletime = 0, basetime = 0;
struct tcf_gate_params *p;
s32 clockid = CLOCK_TAI;
struct tcf_gate *gact;
struct tc_gate *parm;
int ret = 0, err;
- u64 basetime = 0;
u32 gflags = 0;
s32 prio = -1;
ktime_t start;
@@ -375,11 +370,8 @@ static int tcf_gate_init(struct net *net, struct nlattr *nla,
spin_lock_bh(&gact->tcf_lock);
p = &gact->param;
- if (tb[TCA_GATE_CYCLE_TIME]) {
- p->tcfg_cycletime = nla_get_u64(tb[TCA_GATE_CYCLE_TIME]);
- if (!p->tcfg_cycletime_ext)
- goto chain_put;
- }
+ if (tb[TCA_GATE_CYCLE_TIME])
+ cycletime = nla_get_u64(tb[TCA_GATE_CYCLE_TIME]);
if (tb[TCA_GATE_ENTRY_LIST]) {
err = parse_gate_list(tb[TCA_GATE_ENTRY_LIST], p, extack);
@@ -387,14 +379,19 @@ static int tcf_gate_init(struct net *net, struct nlattr *nla,
goto chain_put;
}
- if (!p->tcfg_cycletime) {
+ if (!cycletime) {
struct tcfg_gate_entry *entry;
ktime_t cycle = 0;
list_for_each_entry(entry, &p->entries, list)
cycle = ktime_add_ns(cycle, entry->interval);
- p->tcfg_cycletime = cycle;
+ cycletime = cycle;
+ if (!cycletime) {
+ err = -EINVAL;
+ goto chain_put;
+ }
}
+ p->tcfg_cycletime = cycletime;
if (tb[TCA_GATE_CYCLE_TIME_EXT])
p->tcfg_cycletime_ext =
@@ -408,14 +405,7 @@ static int tcf_gate_init(struct net *net, struct nlattr *nla,
gact->tk_offset = tk_offset;
hrtimer_init(&gact->hitimer, clockid, HRTIMER_MODE_ABS_SOFT);
gact->hitimer.function = gate_timer_func;
-
- err = gate_get_start_time(gact, &start);
- if (err < 0) {
- NL_SET_ERR_MSG(extack,
- "Internal error: failed get start time");
- release_entry_list(&p->entries);
- goto chain_put;
- }
+ gate_get_start_time(gact, &start);
gact->current_close_time = start;
gact->current_gate_status = GATE_ACT_GATE_OPEN | GATE_ACT_PENDING;
--
2.26.2
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